Cutter link for saw chain



April 30, 1968 E. H. HILL 3,380,496

CUTTER LINK FOR SAW CHAIN Filed Oct. 20, 1965 INVENTOR. EM I L H. HILL g d WM United States Patent 3,380,496 CUTTER LINK FOR SAW CHAIN Emil H. Hill, 6316 SE. 65th Ave., Portland, Oreg. 97206 Filed Oct. 20, 1965, Ser. No. 498,300 1 Claim. (Cl. 143-135) ABSTRACT OF THE DISCLOSURE A chisel bit type cutter link for a saw chain made by bending a flat strip of metal having a bevelled edge portion. The bevelled surface on the strip forms the top face of the top plate portion of the cutter. This reduces the bending angle so that a high carbon or stainless steel may be formed by a simple and inexpensive stamping operation instead of the costly investment casting process heretofore required for such steels.

This invention relates to improvements in cutter links for saw chains and an improved method of making the links.

It has heretofore been impossible to make high carbon or stainless steel chisel bit type cutter links by the economically advantageous stamping method. Chisel bit type cutters have a right angle corner between side plate and top plate portions normally requiring a 90 bend of the metal plate in the stamping process. High carbon and stainless steels are cracked or weakened in forming such a bend. As a result, low cost stamped cutters are conventionally made in less desirable curved or curled configurations which lack the recognized advantages of the chisel bit type of cutter. It has heretofore been possible to make high quality chisel bit cutters only by a high cost investment casting process.

Another disadvantage of conventional chisel bit cutters is that it is so diflicult to sharpen them properly. The average user cannot maintain his saw chain in the good condition in which he received it from the manufacturer. The highly eflicient performance of which a good saw chain is capable is quickly lost through improper sharpening whereby the average saw chain operates at relatively low etficiency throughout most of its normal life.

Objects of the invention are, therefore, to provide a high quality cutter which can be manufactured at low cost, to provide a form of chisel bit cutter which can be successively stamped from high carbon and stainless steels, to provide an improved method for making chisel bit cutters, to provide a chisel bit cutter which is easy to sharpen, to provide a cutter having a built-in filing guide, and to provide an improved file for sharpening the cutters.

Important advantages are attained through a new and improved process for making the cutters. The cutters are stamped from a steel strip having a bevelled edge. By virtue of the bevelled edge, the angle in the corner between the top plate and side plate portions is reduced to a value which will not result in cracking or weakening of the metal when it is bent in the stamping process. A square corner is produced by making a bend of substantially less than 90. The cutters are provided with a file guide surface to facilitate hand filing and a special form of file is provided which greatly simplifies the sharpening operation.

The foregoing and other objects and advantages will become apparent and the invention will be better understood from the following detailed description with reference to the accompanying drawing which illustrates a preferred embodiment of the invention. Various changes may be made, however, in the details of construction and all such modifications within the scope of the appended claim are included in the invention.

In the drawing:

FIGURE 1 is a perspective view of a cutter link embodying the features of the invention;

FIGURE 2 is a side elevation view;

FIGURE 3 is a top plan view;

FIGURE 4 is an end elevation view;

FIGURE 5 is an end view of the steel strip from which the cutter is stamped;

FIGURE 6 is a cross sectional view of a file for sharpening the cutter;

FIGURE 7 is a view on the line 77 of FIGURE 2, showing how the file is applied to the cutter;

FIGURE 8 is a side elevation view of a portion of a saw chain having the present cutters; and

FIGURE 9 is a top plan view of the saw chain.

The present cutter link is illustrated by way of example in the type of detachable link saw chain disclosed in my United States Patent No. 3,020,942. It is to be understood, however, that the features of the invention are applicable to cutter links for other types of chains and the invention is not limited to this particular type of chain.

As shown in FIGURES 8 and 9, the chain comprises right-hand cutter links 10, left-hand cutter links 11, drive links 12 and connector links 13. These links are pivotally connected together by rivets 14. Each rivet has one end 15 fixedly secured in a connector link and has a vertically elongated T-head 16 on its opposite end. There are connector links on the opposite sides of the chain interconnecting the drive links and cutter links as shown. This arrangement places the drive links and cutter links in a common vertical plane and each drive link and cutter link is equipped with a tongue 17 which rides in the groove of the saw bar as is well understood in the art. The tongues 17 are shaped to fit a drive sprocket wheel at one end of the saw bar for driving the chain in the direction of the arrow in FIGURE 8.

The vertically elongated rivet heads 16 are adapted to pass through horizontally elongated holes 13 in the drive links and cutter links when one of the links is turned at right angles to the direction of the chain. When the chain is straightened out as shown, the T-heads 16 overlap the side faces of the drive links and cutter links to hold the parts in assembled relation. Behind the heads 16 the rivets have cylindrical bearing surfaces which fit the ends of the elongated holes 18 when the chain is tensioned. For convenience of illustration, the chain is not tensioned in FIGURE 8, the rivets appearing in the centers of elongated holes 18.

A right-hand cutter link 10 is illustrated in FIGURES 1-4, it being understood that each left-hand cutter link 11 is a mirror image of the link 10. Each cutter link has a body portion 20 which contains the holes 18 and is flat in the vertical plane of tongue 17. Extending along the top of body portion 20 is a longitudinal bend line 21 which forms an inclined shank portion 22. Shank 22 assumes an angle of approximately 30 with respect to body 20, although this angle is not critical. A second longitudinal bend line 23 establishes a vertical, or approximately vertical, side plate portion 24 offset from body portion 20. Another longitudinal bend line at 25 forms a top plate portion 26 having a top face at right angles to side plate portion 24.

The leading edge of side plate portion 24 is bevelled on its inner side by filing to form a vertical cutting edge 27 and the leading edge of top plate portion 26 is similarly bevelled on its under side to form a cutting edge 28. This bevel extends around the bend or corner at 25 to form a continuous sharpened cutting edge. This general configuration is characteristic of chisel bit cutters although it is not necessary for the body portions 20 to be aligned with the drive links 12 and equipped with sprocket tongues 17.

In order to make the top face of top plate portion 26 perpendicular to the vertical plane of side plate portion 24, a right angle bend would normally be required to form the link in the usual manner by a stamping process from fiat plate stock. Since high carbon tool steel or stainless steel will become cracked or weakened with such a degree of bending in the stamping process, cutters of such materials having a right angle bend at this point heretofore could not be made by a stamping process but have had to be made by the exceedingly more expensive investment casting process.

According to the present invention, this problem is solved by using a bevelled edge plate which will produce the desired right angle relationship between the top face of top plate portion 26 and side plate portion 24 with considerably less than a right angle bend, which does not crack or weaken the material. Such a bevelled plate 30 is shown in end view in FIGURE having a bottom square edge 31 and a top bevelled edge with a bevelled surface 32 which makes an angle at 33 of approximately 17 with the plane of the plate. Such plate is produced in long strip form and cut off in lengths equal to the length of the cutter link.

In the stamping process the lower edge 31 forms the tongue portion 17 and the bevelled surface 32 forms the top face of top plate portion 26 as shown in FIGURE 4. The angle of bevel is related to the thickness of the plate so that the width of bevelled surface 32 in FIGURE 5 is equal to the desired width of the top face in FIGURE 4 and the bend line 25 is formed on the heel line 25a of the bevel. Thus, the bending angle 35 is reduced by the amount of the angle of bevel 32 whereby the bending angle equals 90 minus 17 or 73. This is illustrated by showing in dotted lines in FIGURE 4 the material removed in forming the bevel 32 in FIGURE 5. High carbon and stainless steels will successfully withstand this degree of bend without cracking or weakening the material whereby they may be stamped successfully and do not have to be made as investment castings.

In order to provide the necessary relief for travelling through the saw kerf, side plate portion 24 is preferably formed with a small clearance angle 40 as shown in FIG- URE 3 and top plate portion 26 is formed with a small clearance angle 41 as shown in FIGURE 2. The angles 40 and 41 are preferably approximately 2 /2 Another important feature of the present cutter is the provision of a rearwardly inclined file guide surface or edge 45 which extends forward in a line from point 46 on bend line 23 at the base of cutting edge 27 to a rounded top corner 47 at the forward end of the link. The peak of corner 47 forms a depth gauge for the cutter when depth gauges are desired.

A special triangular file 50 as shown in FIGURE 6 is used for sharpening the cutters. This file has a smooth bottom surface 51 to slide freely on guide surface 45 and cutting surfaces on rounded corners 52 and the sloping top surfaces 53. The file is applied to the cutter as shown in FIGURE 7, the rounded corner 52 forming the cutting edge at 27 and in the corner at bend line 25 and a fiat top surface 53 forming the cutting edge 28 with the file being stroked at an angle of approximately 45 with the vertical plane of body portion 20. Top surfaces 53 of the file make an angle of approximately 20 with the bottom surface 51. For cutters of average size, the radius of the corners 52 is approximately inch but this would vary with the dimensions of the cutters. In cross section the shape of the file is an isosceles triangle with rounded base corners.

File guide surface 45 makes it extremely easy for even an inexperienced operator to sharpen the cutters. This guide surface holds the file at the proper level in the initial re-sharpening so that it will not be too low or too high. The operator is only required to give attention to holding the file at 45 to the vertical plane of the chain. Since the bottom surface 51 of the file does not cut downward, this surface follows bend line 23 and the file maintains its proper height relation to the top plate portion 26 as the corner 52 cuts rearward in side plate portion 24. Bend line 23 is parallel with top plate portion 26. The saw chain may thus be maintained in substantially its original new condition without the use of separate filing guides and measuring devices which are difficult for an inexperienced operator to use and normally entail some additional expense.

Having now described my invention and in what manner the same may be used, what I claim as new and desire to protect by Letters Patent is:

1. A high carbon or stainless steel chisel bit type cutter link having a top plate portion with a top face extending perpendicular to a side plate portion of the link, comprising a fiat strip of said steel having one edge bevelled on one side of the strip, the width of the bevelled surface being equal to the width of said top face, longitudinal bends in said strip forming a body portion and said side and top plate portions, the surface of said bevel forming said top face, the bend connecting said side plate and top plate portions being located on the heel line of the bevel, and the angle of bend between said side plate and top plate portions being less than by an angle equal to the angle of said bevel, said side and top plate portions having forward cutting edges adapted to be sharpened by hand filing, and an inclined file guide surface on the link extending in a straight line forward from said cutting edges to the leading end of the link.

References Cited UNITED STATES PATENTS 358,026 2/1887 Emerson 29-78 2,854,866 10/1958 Mall et al 76112 3,144,891 8/1964 Carlton l43135 3,269,434 8/1966 Cooper 143-135 WILLIAM W. DYER, 1a., Primary Examiner.

GRANVILLE Y. CUSTER, JR., Examiner. 

